Garmin GNS 400W Series Maintenance Manual page 53

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Audio Distortion
The receiver audio distortion at rated audio output when modulated 85% with a tone from 350 -
2500 Hz with RF level at 10,000 µV and the compressor enabled, shall not exceed 25% when
measured at 350 Hz. Additionally, the distortion shall not exceed 15% when measured at 1000
Hz and 2500 Hz.
1. Enable the compressor.
2. Set the test set for 127 mHz RF carrier, 85% modulation, modulation frequencies of
350 Hz, 1 kHz, and 2.5 kHz. Set the output level to 10,000 µV.
3. Set the volume for rated audio level.
4. Measure the audio distortion and verify the following:
350 Hz: distortion < 25%
•
1000 Hz: distortion ≤ 15%
•
2500 Hz: distortion ≤ 15%
•
Signal Pin Signal Name
J2-7 COMM AUDIO HI
Microphone Intercom
The audio level shall not be less than 7.07 Vrms when a 125 mVrms signal at 1000 Hz is applied
between INTERCOM MIC J2-5 and INTERCOM MIC LO J2-17 and the receive audio is
squelched. The audio distortion shall be less than 10% when a 125 mVrms signal at 1000 Hz is
applied between the INTERCOM MIC, J2-5 and INTERCOM MIC LO J2-17 input and the
receive audio is squelched.
1. Enable the compressor.
2. Turn the carrier off.
3. Send a 1 kHz audio signal to the intercom microphone input of unit.
4. Set the volume to a minimum level and verify the following:
Microphone intercom audio level ≥ 7.07 Vrms
•
Microphone intercom distortion < 10%
•
Signal Pin Signal Name
J2-7 COMM AUDIO HI
GNS 400W Series Maintenance Manual
190-00356-05
Reference Pin Reference Name
J2-19 COMM AUDIO LO
Reference Pin Reference Name
J2-19 COMM AUDIO LO
Load
500 Ohms
Load
500 Ohms
Page 4-27
Rev. A